Method of and adjuvant powder for thermochemical material removal from refractory materials



United States Patent O METHOD OF AND ADJUVANT POWDER FOR THERMOCHEMICAL MATERIAL REMOVAL FROM REFRACTORY MATERIALS Edward M. Holub, Plainfield, N. J.

No Drawing. Application May 1, 1956 Serial No. 581,847

14 Claims. (Cl. 148-9) The present invention relates to a novel process for thermochemically removing material from metal or alloy bodies which are resistant or immune to such removal by the conventional procedure of impinging only flame and an oxygen jet against the surface to remove material therefrom, and additionally, relates to a novel adjuvant powder composition useful in the novel process.

Certain metal and alloy bodies are immune or resistant to the thermochemical removal of material therefrom by the action of preheating flames and a stream or jet of oxygen. Examples of such oxidation resistant bodies are certain ferrous metals, such as stainless steel and cast iron, certain non-ferrous metals, such as copper, aluminum and nickel, and many corrosion and oxidation resistant alloys, such as nickel-base alloys containing molybdenum, nickel-base alloys containing molybdenum and chromium, cobalt-chromium-tungsten alloys, and various siliconbronzes. Such metals and alloys which are immune or resistant to material removal by the conventional thermochemical metal-removing action of preheating flames and a stream or jet of oxygen are hereinafter referred to as refractory bodies.

A process has been proposed for removing material from such refractory bodies by employing a heating flame and a finely-divided combustible adjuvant material-carrying oxygen stream distinct from but flowing along side of the flame. In accordance with that process, as disclosed and claimed in U. S. Patent No. 2,451,422 to R. L. Wagner, entitled, Thermochemical Removal of Metal with a Flux-Forming Powder in the Oxygen Cutting Stream, and U. S. Patent No. 2,598,025 to R. L. Wagner and entitled, Thermochemical Cutting and Scarfing Powder, the finely-divided adjuvant material is burned in the oxygen stream to provide the additional heat necessary to bring the surface of the refractory body to a temperature at which thermochemical removal of material is accomplished by the oxygen stream, and additionally, to form composition products which flux the refractory metallic oxide and provide a removable fluid mixture of oxides. The adjuvant powder material employed in accordance with such process consisted mainly of iron, the'balance containing incidental impurity materials. While such process provided the first effective method for thermochemical removal of material from refractory bodies, it required the use of costly iron powder and'relatively low processing speeds, as compared to those encountered in the thermochemical removal of metal by conventional processes employing preheating flames and a stream or jet of oxygen alone.

Another process has been proposed for thermochemically removing material from refractory bodies by the employment of an adjuvant powder mixture containing between and 65 percent by weight aluminum metal,

and the balance iron powder. Such process is disclosed and claimed in U. S. Patent No. 2,632,721 issued to E. Meincke and entitled, Powder Cutting and Scarfing of Resistant Metallic Bodies. This adjuvant powder mixture containing aluminum, upon combustion in the oxygen stream, serves to elevate the temperature of the surface of the refractory body to temperatures not obtainable in the use of adjuvant iron powder alone. However, the cost of such aluminum-iron powder mixture is extremely high for the increase in processing speed obtained over iron powder alone in the Wagner process, discussed hereinabove. In addition, the slag formed in this process is not readily removed from the surface of the metal body.

It is the main object of the present invention to provide a process for powder cutting and scarflng refractory bodies in which improved slag removal characteristics are obtainable; and to provide a novel adjuvant powder composition useful in such novel process, which powder composition is relatively inexpensive and gives a reduced heateffected zone without any reduction in process cutting speed.

Other aims and advantages of the invention will be apparent from the following description and appended claims.

In accordance with the present invention, a process is provided for powder cutting and scarfing refractory bodies which comprises, heating a portion of the body with an oxy-fuel flame, and concurrently directing against the heated portion of the body a stream of oxidizing gas and a stream of adjuvant powdered mixture containing between 10 and percent by weight quartz-containing material. The remainder may contain metallic iron, metallic aluminum, and/or other oxidizable metallic powders.

More specifically, material is thermochemically removed from the refractory body by applying an oxidizing gas jet against a heated zone of action on the surface of the body while concurrently flowing a stream of finelydivided adjuvant material, composed principally of quartzcontaining material, such as quartz, sand, rock crystal and the like, and oxidizable metallic powders, such as iron, aluminum, and the like, or mixtures thereof, into the zone of action so as to oxidize the oxidizable constituents of the body and produce reaction products sufliciently fluid to be expelled by the force of the oxidizing gas jet and the abrasive action and force of the adjuvant material stream.

The elemental metallic powder component or components of the adjuvant powder mixture burn readily in oxygen to liberate intense heat and form compounds which aid in fluxing the refractory oxides. The quartzcontaining component of the adjuvant material also aids in fluxing the refractory oxides, and additionally, serves to remove slag by an abrasive action.

Accordingly, the use of the novel adjuvant powder mixture of the process of the invention produces thermochemical material removal from refractory bodies in which a very rapid removal of slag from the heat-effected zone is possible, thereby minimizing the extent of the heat effected zone. This result is accomplished without lowering the cutting speeds below values heretofore obtainable, and while at the same time employing a much less expensive powdered mixture.

It has been found that the use of powder mixtures containing greater than 80% by weight quartz-containing material does not produce satisfactory results. This is believed due to the provision of an insufficient amount of exothermically oxidizable metal constituent. On the other hand, the use of powder mixtures containing less than 10% by weight of quartz-containing material and the balance iron powder does not produce cutting results improved to any significance over those obtained with the use of iron powder.

The process of the present invention may be employed for cutting and scarfing refractory bodies, and such procedures generically include operations known to the art as: severing, deseaming, surface conditioning, gouging,

desurfacing, powder washing, and the like, which operations are specific applications of the powder cutting and scarfing processes.

Successive portions of the refractory body on a path extending along a surface can be thermochemically removed by effecting a steady and continuous relative movement of travel between the body and the streams of oxygen and adjuvant material across the heated surface. Heating of the zone of action is accomplished by oxyfuel flames, preferably oxy-acetylene flames. In flame machining operations wherein only material near the surface is removed, a sufficiently fluid reaction product is one which can be blown ahead of the reaction zone by the oxygen and adjuvant material streams to expose a fresh material surface to the streams, and to preheat the surface portion to be removed next. In cutting operations, such as severing, sufficiently fluid reaction products are those which can be blown through and out of the kerf, thus exposing fresh material surfaces against which the jets impinge.

Flame machining to remove surface material is carried out by advancing along the surface in the direction of a gas flow a low velocity oxygen jet directed obliquely at a small angle against successive heated zones on the surface of the body, while introducing the novel finelydivided material into the successive zones. Here also, heating is preferably accomplished by applying one or more oxy-acetylene flames to the surface. In this procedure the oxygen jet velocity generally is maintained less than 980 ft./sec. (the acoustic velocity in oxygen) as it leaves the blowpipe nozzle.

In flame severing or other cutting operations a high velocity oxygen jet preferably flowing at or above the acoustic velocity is directed at a large angle, such as 90, against the hot refractory body, while continuously introducing the finely-divided adjuvant material into the reaction zone where the oxygen impinges. In severing, the oxygen jet passes completely through the body and forms a deep kerf which is advanced along a selected path by steadily advancing the oxygen jet so as to im-. pinge against successive heated zones of the body. If a kerf extending only partly through the body is desired, the jet is advanced at a rate rapid enough to prevent complete penetration.

Apparatus such as disclosed in U. S. Patents 2,451,422 to R. L. Wagner or 2,626,880 to E. Mcincke may be suitably employed for performing the process of this invention in a refractory body cutting application, whereas apparatus such as disclosed in U. S. Patent 2,622,048 to F. Moesinger may be suitably employed for performing the process of the invention in a refractory body scarfing application.

In further accordance with the present invention, the novel finely-divided adjuvant material is carried into the reaction zone in close association with the metal-removing oxidizing gas itself. The adjuvant material may be added to and carried by the stream of oxidizing gas in the blowpipe apparatus, in the manner described in U. S. Patent 2,451,422, or may be concurrently introduced into the reaction zone as a stream separate from the oxidizing gas stream, intermixing of the two streams being effected in the region of the reaction zone, in the manner disclosed in U. S. Patent 2,626,880. It has been found that the latter procedure is preferable since it does not introduce the problem of erosion of the oxidizing gas passages in the blowpipe, which effect is encountered where the oxidizing gas stream is employed as a carrier for the adjuvant powder stream.

Various types of quartz-containing sands as well as substantially pure quartz have been employed successfully in the process of the present invention. Cowbay sand, quartz, and silica foundry sand have been found to possess excellent flow characteristics and produce excellent cut and scarfed surface qualities.

It has been found that the particle size of the particulate components of the adjuvant powder mixture is important to the quality of the cut as well as to the flow characteristics encountered in the handling of the stream of adjuvant material. Quartz-containing materials of fine particle size do not produce the most desirable results in either cutting or scarfing operations, since, while they do provide good starts, they do not allow deep penetration of the refractory body. Quartz-containing materials of coarse particle sizes permit full-cut penetration but do not provide good starts.

A quartz-containing material particle sizes substantially distributed over the range of from about 30 to 100 mesh may be employed in the method of the invention in either powder cutting or scarfing applications to produce good starts with good penetration. It is believed that the need for relatively large size particles of quartz-containing material in the adjuvant material mixture indicates that, in cutting, an erosive action is responsible for the effectiveness of this constituent of the adjuvant powder material. It has been found, in keeping with this belief, that a standard quartz-containing material particle sizes such that 100 percent passed through 30 mesh, percent held on 60 mesh (i. e.30, 90% +60) produced the best cutting results.

It has also been found that the particle size of the iron and/ or aluminum or other oxidizable metal powder constituent of the flowable adjuvant powder mixture of the invention also effects the quality of the cut and speeds obtainable in the operation of the process of the invention. For example, iron powder particles sized between 30 and 200 mesh give good penetration but poor starts; iron powder particles sized between 200 and 325 mesh started satisfactorily and produced satisfactory material removal but required powder flow and pressure conditions which were rather critical. Iron powder particles sized finer than 325 mesh give good starts, but provide poor cut penetration in the process. Accordingly, it was found preferable to employ oxidizable metal component powders having particle sizes distributed over the range from 30 mesh to finer than 325 mesh to obtain the desirable qualities of each of the particle size ranges. Such powders are hereinafter referred to as standard powders.

It has been found undesirable to employ greater than 5% aluminum in the novel powder mixture of the invention for thermochemically removing material from ironcontaining material bodies. This is believed due to the burning up of other constituents of the mixture by the combustion of aluminum to result in lowering the efficiency of the cutting or scarfing operation.

The following Table I sets forth operating data obtained in cutting employing two different powder mixtures in accordance with the invention, as well as data obtained in cutting employing percent iron powder of the prior art. In each instance the apparatus employed was of the general type disclosed in U. S. Patent No. 2,626,880, issued January 27, 1953 to E. Meincke.

As is apparent from the data set forth in Table I above, cuts were obtained using the sand-iron adjuvant mixture of the invention at cutting speeds equal to those obtained employing up to more than twice the iron powder content. Additionally, tests showed that the quality of 5 outs obtained with the mixtures of the invention were uniformly at least as good and in most cases better than those obtained employing 100 percent iron powder. Further, slag removal was much more eifective when employing The following Table II sets forth the chemical analysis of cutting slag obtained in the cutting of Type 18-8 stainless steel employing a 70% sand-30% iron powder mixture, a 50% sand-50% iron powder mixture, and a the novel mixtures of the invention. sand-100% iron powder mixture.

.TABLE II Analysis of cutting slag from type 18-8 stainless steel Percent Sample No.

Silicon Chro- Chro- Nickel Iron Ratios of Silicon Dioxide mium Nickel Oxide Iron Oxide Samples 1. (70%-30% Sand-Iron):

Metallic 0.01 0.89 12 5 70.7 36.4 Non-Metallic..- 6.65 30. 1 0.87 58.0 63.6 2. (50%50% Sand-Iron):

Metallic 0.07 2. 34 12 5 73.8 38.9 Non-Metallic 3.12 29. 4 1. 04 61. 9 61. 1 3. (0%100% Sand-Iron):

Metallic 0. 01 11 7 78.4 26.5 Non-M lli 0.65 32.8 1 08 62.2 73.5

Notes The portion of the sample specified metallic contains considerable non-metallic; hence the failure to total close to 100 percent; the non-metallic portions contain only small amounts of metallics.

It is not possible to determine the ferrous iron content of the non-metallic portion because of its refractory nature; however,

the iron is likely present as iron oxide.

less steel with apparatus sim 30 Patent 2,626,880.

ilar to that disclosed in U. S.

TABLE III Run Iron Alnmi- Particle Mesh Size No. Quartz Type Percent Percent num Distribution Cutting Results Percent 1 Silica Foundry (Fine).. 50 50 gfgi ggghgggt pgt }Erratic.

Sand60 907+l00 2 60 4O {rondstenilgr an 0, 0 3 40 60 {lrondstgndkard i i an 0 100 Silica Foundry 50 s d i }G d.

an 30 100 60 irondstagrgiaird an 00 70 {gon stangarlovq fianu ilar z 90 {A1uminum 206+400 }Unsatisfactory.

Quartz-30, 9075-1-60... 80 10 10 Iron standard Do.

Aluminum200+400. Quartz30, 90%+60. 69 1 Iron standard Good.

glHg1lD6HIIg;qiO -|4OO E an 0, 0 100 rraticoor S111 Foundry 70 30 {Iron standardi penetra t ion Silica Foundry (Coarse)... 60 {ifgfgggg }Unsatisfactory.

Sand14+60 50 {Iron standard Silica Foundry-.- 50 50 }Good.

Sand30, 907 +100 70 30 Iron standard 100 0 }Unsatisfaetory.

Quartz-30, 907+60. 90 10 {Iron standard 80 }Erratic. 70 }Good.

D0 40 Q, t 30 5 07-1-60 DO uar z- 30 gon stangdQargii... D

uar z 60. 25 Iron standard 20 {Quartz-30, 90%+60 D0 15 Do. 10 Do. 70 30 }Unsatisfactory. 70 30 }Erratic. 70 so }Unsatisfact0ry.

TABLE III-Continued Run Iron Alumi- Particle Mesh Size No. Quartz Type Percent Percent num Distribution Cutting Results Percent 30 Quartz 50 {Quartz-30, 90%+60. Erratic.

Iron-200+325 31 d 80 Quartz30, 90%+60 }Unsatisfactory.

Iron325 32. d0 85 figuring-30, 90%+60 D0.

ron- 33 d0 90 10 Quartz-30, 90%+60 D0.

Iron-325 34 d0 70 30 Good.

60 40 Do. 70 30 Do.

80 Erratic.

Sand-30, 907 +60, 70 so 10% 325l 0 }Good.

Iron standard As employed in Table III, the term erratic" is employed to describe results where cutting obtained was not consistently good due either to the use of a powder mixture outside of the composition range of the invention or to the use of too coarse or too fine quartz-containing particles. The term unsatisfactory is employed to describe results where flying starts could not be obtained with that powder mixture.

Under many conditions an unbonded thermochemical refractory body cutting and scarfing adjuvant powder mixture may be employed. However, where the powder mixture contains a mixture of quartz-containing powders and oxidizable metal powders and is to be stored for long periods of time before use or transported to the point of use, undesirable segregation of the constituents of the mixture may be encountered. In order to avoid this, a bonding agent may beemployed in small quantities to prevent segregation. Mineral oils, vegetable oils and, in fact, any sticky non-reactive material, may be employed to bond the powder mixture to eliminate segregation. In one example, a sand-iron powder mixture (30, 90% +60 mesh sand and standard iron powder) was bonded with one part of SAE-ZO motor oil to 450 parts by weight of the mixture. Such a bonded mixture overcame the segregation problem and provided an easily flowable bonded adjuvant powder mixture which was successfully employed in thermochemically removing material from a refractory body.

What is claimed is:

l. A flowable thermochemical refractory body cutting and scarfing adjuvant powder mixture containing between 10 and 80 percent by weight abrasive material predominantly containing quartz and having particle sizes substantially distributed between about and 100 mesh and the remainder at least one oxidizable metal powder selected from the group consisting of iron powder and aluminum powder.

2. A flowable thermochemical refractory body cutting and scarfing adjuvant powder mixture consisting essentially of between 10 and 80 percent by weight abrasive material predominantly containing quartz and having particle sizes substantially distributed between about 30 and 100 mesh, and the remainder at least one oxidizable metal powder selected from the group consisting of iron powder and aluminum powder, the particle size of said abrasive material predominantly containing quartz being larger than that of said oxidizable metal powder.

3. A flowable thermochemical refractory body cutting and scarfing adjuvant powder mixture containing between 10 and 80 percent by weight sand material having particle sizes Substantially distributed between about 30 and 100 mesh, and the remainder at least one oxidizable metal powder selected from the group consistin of iron powder and aluminum powder having particle sizes distributed over the range from 30 mesh to finer than 325 mesh.

4. In the process of thermochemically removing material from a refractory body, wherein a stream of oxidizing gas and adjuvant powdered material are concurrently directed against a heated zone of such body, the improvement which comprises contributing abrasive action to said metal removal by employing as said adjuvant powdered material a mixture containing between 10 percent by weight and percent material predominantly containing quartz and having particle sizes substantially distributed between about 30 mesh and mesh and the remainder at least one oxidizable metal powder selected from the group consisting of iron powder and aluminum powder.

5. In the process of thermochemically removing material from a refractory body, wherein a stream of oxidizing gas and adjuvant powdered material are concurrently directed against a heated zone of such body, the improvement which comprises employing as said adjuvant powdered material a mixture containing between 10 percent and 80 percent by weight abrasive material predominantly containing quartz and the remainder at least one elemental oxidizable metallic powder selected from the group consisting of iron powder and aluminum powder, the particle sizes of said quartz-containing constituent being substantially distributed between about 30 mesh and 100 mesh, the particle size of said quartz-containing material being larger than that of said oxidizable metal powder.

6. The method of thermochemical removal of material from a refractory body which comprises directing against said body at least one preheating flame envelope to heat a portion of said body, directing at least one stream of material-removing oxidizing gas against the heated portion of said body, and concurrently directing at least one stream of adjuvant powdered material against said heated portion of said body, said adjuvant powdered material containing a mixture of between 10 percent and 80 percent by weight sand having particle sizes substantially distributed between about 30 mesh and 100 mesh and the emainder at least one oxidizable metal powder selected from the group consisting of iron powder and aluminum powder having particle sizes distributed over the range from 30 mesh to finer than 325 mesh.

7. The method of thermochemical removal of material from a refractory body which comprises directing against said body at least one preheating flame envelope to heat a portion of said body, directing at least one stream of material-removing oxidizing gas against the heated portion of said body, and concurrently directing at least one stream of adjuvant powdered material against said heated portion of said body, said adjuvant powdered material containing a mixture of between 10 percent and 80 percent by weight material predominantly oontaining quartz and the remainder at least one oxidizable metal powder selected from the group consisting of iron powder and aluminum powder, the particle size of said quartzcontaining material being larger than that of said metallic powder and substantially distributed between about 30 mesh and 100 mesh.

8. An unbonded flowable thermochemical refractory body gas borne cutting and scarfing adjuvant powder mixture containing between and 80 percent by weight material predominantly containing quartz and the remainder at least one oxidizable metal selected from the group consisting of iron powder and aluminum powder, said predominantly quartz-containing material having particle sizes larger than those of said metal and substantially distributed between about 30 and 60 mesh.

9. A bonded flowable thermochemical refractory body gas borne cutting and scarfing adjuvant powder mixture containing a small quantity of a bonding agent and between 10 and 80 percent by weight material predominantly containing quartz and the remainder at least one oxidizable metal selected from the group consisting of 7 iron powder and aluminum powder, said predominantly quartz-containing material having particle sizes larger than those of said metal and substantially distributed between about 30 and 100 mesh.

10. In the process of thermochemicallyremoving material from a refractory body, wherein a stream of oxidizing gas and adjuvant powdered material are concurrently directed against a heated zone of such body, the improvement which comprises contributing abrasive action to said material removal by employing as said adjuvant powdered material a mixture containing between 10 percent and 80 percent by weight material predominantly containing quartz and having particle sizes substantially distributed between about 30 mesh and 100 mesh and the remainder at least oneoxidizable metal powder selected from the group consisting of iron powder and aluminum powder, the particle size of said material predominantly containing quartz being larger than that of said oxidizable metal powder.

11. In the process of thermochemically removing material from a refractory body, wherein a stream of oxidizing gas and adjuvant powdered material are concurrently directed against a heated zone of such body, the improvement which comprises contributing abrasive action to said material removal by employing as said adjuvant powdered material a mixture containing between 10 percent and 80 percent by weight material predominantly containing quartz and the remainder at least one oxidizable metal powder selected from the group consisting of iron powder and aluminum powder, the particle size of said material predominantly containing quartz being larger than that of said oxidizable metal powder and substantially distributed between about 30 mesh and 100 mesh.

12. The method of thermochemical and abrading removal of material from a refractory body which comprises directing against said body at least one preheating flame envelope to heat a portion of said body, directing at least one stream of material-removing oxidizing gas against the heated portion of said body, and concurrently directing at least one stream of adjuvant and abrasive powdered material against said heated portion of said body, said adjuvant and abrasive powdered material containing a mixture of between 10 percent and percent by weight material containing predominantly quartz and having particle sizes substantially distributed between about 30 mesh and mesh, and the remainder at least one oxidizable metal powder selected from the group consisting of iron powder and aluminum powder.

13. The method of thermochemical and abrading removal of material from a refractory body which comprises directing against said body at least one preheating flame envelope to heat a portion of said body, directing at least one stream of material-removing oxidizing gas against the heated portion of said body, and concurrently directing at least one stream of adjuvant and abrasive powdered material against said heated portion of said body, said adjuvant and abrasive powdered material containing a mixture of between 10 percent and 80 percent by Weight material containing predominantly quartz and having particle sizes substantially distributed between about 30 mesh and 100 mesh, and the remainder at least one oxidizable metal powder selected from the group consisting of iron powder and aluminum powder.

14. The method of thermochemical and abrading removal of material from a refractory body which comprises directing against said body at least one preheating flame envelope to heat a portion of said body, directing at least one stream of material-removing oxidizing gas against the heated portion of said body, and concurrently directing at least one stream of adjuvant and abrasive powdered material against said heated portion of said body, said adjuvant and abrasive powdered material containing a bonded mixture of between 10 percent and 80 percent by weight material containing predominantly quartz and having particle sizes substantially distributed between about 30 mesh and 100 mesh, and the remainder at least one oxidizable metal powder selected from the group consisting of iron powder and aluminum powder.

References Cited the file of this patent UNITED STATES PATENTS 1,506,246 McMahon Aug. 26, 1924 2,415,815 Deming Feb. 18, 1947 2,451,422 Wagner Oct. 12, 1948 2,470,999 Meincke May 24, 1949 FOREIGN PATENTS 160,479 Australia Apr. 24, 1952 

4. IN THE PROCESS OF THERMOCHIMICALLY REMOVING MATERIAL FROM A REFRACTORY BODY, WHEREIN A STREAM OF OXIDIZING GAS AND ADJUVANT POWDERED MATERIAL ARE CONCURRENTLY DIRECTED AGAINST A HEATED ZONE OF SUCH BODY, THE IMPROVEMENT WHICH COMPRISES CONTRIBUTING ABRASIVE ACTION TO SAID METAL REMOVAL BY EMPLOYING AS SAID ADJUVANT POWDERED MATERIAL A MIXTURE CONTAINING BETWEEN 10 PERCENT BY WEIGHT A MIXTURE CONTAINING BETWEEN 10 PERCENT BY QUARTZ AND HAVING PARTICLE SIZES SUBSTANTIALLY DISTRIBUTED BETWEEN ABOUT 30 MESH AND 100 MESH AND THE REMAINDER AT LEAST ONE OXIDIZABLE METAL POWDER SELECTED FROM THE GROUP CONSISTING OF IRON POWDER AND ALIMUNUM POWDER. 